1. Field of the Invention
This invention relates to an electrostatic capacity type touch sensor.
2. Description of the Related Art
The electrostatic capacity type touch sensor has been known as a data input device to various kinds of electronic devices such as a mobile phone, a portable audio device, a portable game console, a television and a personal computer.
The electrostatic capacity type touch sensor detects a touch by detecting a change in a capacitance of a capacitor associated with a touch pad induced by touching or approaching the touch pad with a finger of an operator or a pen tip (hereafter referred to as the finger of operator or the like).
Since an output value of the electrostatic capacity type touch sensor varies sensitively to its environment (temperature, humidity, electric field from its surrounding environment or the like), an offset adjustment to an input or an output of the sensor, which is referred to as calibration, is required in general.
Further information on the electrostatic capacity type touch sensor is disclosed in Japanese Patent Application Publication No. 2005-190950, for example.
It is preferable that the calibration is performed while the finger of operator or the like does not touch the touch pad. It is also preferable that the calibration is performed whenever the environment has changed even slightly.
However, while the change in the environment, to which the electrostatic capacity type touch sensor is vulnerable, occurs frequently in daily usage, the calibration take considerable amount of time. In addition, if the finger of operator or the like touches during the calibration, the situation is reflected in the calibration to make it wrong calibration.
Thus, this invention is directed to offer an electrostatic capacity type touch sensor that can be calibrated in a short period of time at a moment when the finger of operator or the like does not touch the touch pad.